Spectral Classification and Luminosity Function of Galaxies in the Las Campanas Redshift Survey
Abstract
We construct a spectral classification scheme for the galaxies of the Las Campanas Redshift Survey (LCRS) based on a principal component analysis of the measured galaxy spectra. We interpret the physical significance of the spectral classes and conclude that they are sensitive to morphological type and the amount of active star formation. In this first analysis of the LCRS to include spectral types, we find that the general luminosity function for the survey, expressed as a weighted sum of type-specific luminosity functions, exhibits a broad shoulder centered on an absolute magnitude near M = -20 in the R-band, a significant deviation from the Schechter parameterization. At fainter magnitudes, the slope of this luminosity function rises steadily; at M = -17.5 it has a value of alpha = -1.1, steeper than predicted in a type-independent analysis. The luminosity functions of the individual spectral types show a smooth steepening of the faint-end slope from alpha = +0.5 for early types to alpha = -1.9 for late types. We also find that for a given spectral type the luminosity function can depend on environment. Specifically, the faint-end slope in the case of early-type galaxies steepens significantly with increasing local density. These results, coupled with the known density-dependence of the relative populations of galaxy types, may explain the discrepancy between the luminosity functions of the LCRS galaxies and other redshift catalogs such as the Century Survey (Geller et al. 1997). Furthermore, these results have interesting implications for theories of galaxy formation, for they suggest that galaxies of a given type are, on average, fainter when they are located in high-density regions of the Universe.Keywords
All Related Versions
This publication has 0 references indexed in Scilit: